Re: [PATCH 1/6] ARM: spectre-bhb: enable for Cortex-A15

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Hi Ard,

On 28/03/2022 14:47, Ard Biesheuvel wrote:
The Spectre-BHB mitigations were inadvertently left disabled for
Cortex-A15, due to the fact that cpu_v7_bugs_init() is not called in
that case. So fix that.

Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
  arch/arm/mm/proc-v7-bugs.c | 1 +
  1 file changed, 1 insertion(+)

diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c
index 06dbfb968182..fb9f3eb6bf48 100644
--- a/arch/arm/mm/proc-v7-bugs.c
+++ b/arch/arm/mm/proc-v7-bugs.c
@@ -288,6 +288,7 @@ void cpu_v7_ca15_ibe(void)
  {
  	if (check_spectre_auxcr(this_cpu_ptr(&spectre_warned), BIT(0)))
  		cpu_v7_spectre_v2_init();
+	cpu_v7_spectre_bhb_init();
  }
void cpu_v7_bugs_init(void)


Since this patch has been merged, I am seeing a ton of messages when booting Linux on tegra124-jetson-tk1 ...

[ 1233.327547] CPU0: Spectre BHB: using loop workaround
[ 1233.327795] CPU1: Spectre BHB: using loop workaround
[ 1233.328270] CPU1: Spectre BHB: using loop workaround
[ 1233.328700] CPU1: Spectre BHB: using loop workaround
[ 1233.355477] CPU2: Spectre BHB: using loop workaround
** 7 printk messages dropped **
[ 1233.366271] CPU0: Spectre BHB: using loop workaround
[ 1233.366580] CPU0: Spectre BHB: using loop workaround
[ 1233.366815] CPU1: Spectre BHB: using loop workaround
[ 1233.405475] CPU1: Spectre BHB: using loop workaround
[ 1233.405874] CPU0: Spectre BHB: using loop workaround
[ 1233.406041] CPU1: Spectre BHB: using loop workaround
** 1 printk messages dropped **

This is significantly increasing the boot time and causing failures if the boot takes too long.

I see that Dmitry has posted a fix for one of these cases [0], but the above also needs to be fixed.

Thanks
Jon


[0] https://lore.kernel.org/linux-arm-kernel/20220519161310.1489625-1-dmitry.osipenko@xxxxxxxxxxxxx/T/
--
nvpublic



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